Looks good.
Brian
On Sat, Feb 20, 2010 at 3:11 PM, Øyvind Jensen <jensen.oyv...@gmail.com>wrote:
> ---
> sympy/physics/secondquant.py | 29 ++++++++++++++++++++---------
> 1 files changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/sympy/physics/secondquant.py b/sympy/physics/secondquant.py
> index 93f9ca3..858c222 100644
> --- a/sympy/physics/secondquant.py
> +++ b/sympy/physics/secondquant.py
> @@ -2505,27 +2505,38 @@ def _substitute(expr, ordered_dummies,
> arg_iterator, **require):
> Dummies without the keyword in .assumptions0 will be default to
> give the value False.
>
> + Warning
> + =======
> +
> + Apart from checking the keyword requirements, nothing is done to
> prevent
> + loss of information during substitution.
> +
> +
> + Examples
> + ========
> +
> >>> from sympy import Symbol
> - >>> from sympy.physics.secondquant import substitute_dummies,
> _substitute
> + >>> from sympy.physics.secondquant import substitute_dummies,
> _substitute,F
> >>> q = Symbol('q', dummy=True)
> >>> i = Symbol('i', below_fermi=True, dummy=True)
> >>> a = Symbol('a', above_fermi=True, dummy=True)
> -
> >>> reverse = lambda x: reversed(x)
> - >>> _substitute(a, [q], reverse, above_fermi=True) # will succeed
> - _a
> - >>> _substitute(i, [q], reverse, above_fermi=True) # will not
> succeed
> - _i
> - >>> _substitute(i, [q], reverse, above_fermi=False) # will succeed
> - _i
> +
> + >>> _substitute(F(a), [q], reverse, above_fermi=True) # will succeed
> + AnnihilateFermion(_q)
> + >>> _substitute(F(i), [q], reverse, above_fermi=True) # will not
> succeed
> + AnnihilateFermion(_i)
> + >>> _substitute(F(i), [q], reverse, above_fermi=False) # will succeed
> + AnnihilateFermion(_q)
>
> With no keywords, all dummies are substituted.
>
> + >>> _substitute(F(i), [q], reverse) # will succeed
> + AnnihilateFermion(_q)
> """
>
> dummies = _remove_duplicates(_get_dummies(expr, arg_iterator,
> **require))
> subslist = _get_subslist(dummies, ordered_dummies)
> -
> result = expr.subs(subslist)
> return result
>
> --
> 1.6.5
>
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